Emil Levi

Liverpool John Moores University

18th March 2016

Demonstrator 3: Integrated on-board battery charging using multiphase machines and power electronics

Introduction

Charging possibilities for EVs: Wireless battery charging (‘on the move’ and stationary) Wired (plug-in) battery charging using

Single-phase or three-phase mains supply Dc charging stations

Supply options: Two-level inverters/rectifiers Multilevel multiphase inverters/rectifiers

Charger types: On-board charger (recommended)

BUT: Takes space, adds weight, adds cost – when designed as a separate unit.

Concept of integrated on-board charger • Re-use of the propulsion components in the charging process

• No additional space required, no weight added, no cost added.

AC/DC

Using a three-phase machine

Three-phase machine: three-phase (fast) charging with zero torque not possible without additional components; single-phase (slow) charging with zero torque is possible.

Passing three-phase currents through a three-phase motor during charging will not cause rotation since the voltage across the stator is small, but will nevertheless create rotating field and mechanical braking will have to be used.

Current semi-integrated solution (3-phase motor): Renault ZOE

43 kW “Chameleon charger” • Inverter and motor (synchronous, with field

winding) are integrated into the charging process. Dc from junction box charges battery through the neutral point of the 3-phase winding and the negative rail of the dc-link. No reconfiguration required.

• The junction box: 1) manages the charging process; 2) changes the alternating current to direct current; 3) communicates with the charging station.

• The system does require additional power electronic components.

inverter

el. motor

Using a multiphase system instead of a 3-phase one

Advantages of multiphase machines include: Reduced current/power rating per-phase – this is relevant for EVs since, although the power may not be too high, voltage level may be low requiring high current. Additional degrees of freedom, which enable:

Improved fault tolerance (relevant for propulsion operation – ‘limp-home mode’). Integrated on-board battery charging for EVs – as discussed further on, fully integrated on-board battery chargers can be realised, using both three-phase and single-phase supply, with zero torque generation during charging/V2G mode.

A current solution based on multiphase system concept: Valeo

The machine operates as a three-phase one in propulsion mode, but is in essence a symmetrical six-phase machine in charging and V2G modes; in propulsion mode each phase is supplied from an H-bridge inverter.

• Grid terminals are connected to machine windings’ mid-points.

• Field is canceled within each winding – no torque.

• No reconfiguration necessary. • Machine has to be custom made (in essence

symmetrical six-phase machine).

Five-phase topology • Requires hardware reconfiguration, which however consists of only two switches as

additional components. • Phase impedances seen by different grid phases are not all equal (impacts on control). • Space vectors of currents during charging are in the two planes governed with

(pulsating excitation in both planes):

CBAT

hardware

reconfig.

five-phase

machine

three-phase

grididc iL

ic

vdc

S1

S2

iag

ibg

icg

vag+

vcg+

vbg+

vb

vc

vd

ve

va

EMI

filter

(on-

board )

iag

ib

ic

id

ie

ia

ibg

icg

ibg /2

icg /2

iag

icg /2

ibg /2a

b

c

d

e

)659.0cos(2 tIi )659.0cos(2 tIi xy

Asymmetrical six-phase topology • Propulsion: dual three-phase winding with two isolated neutral points, vector control

with two pairs of current controllers. • Charging/V2G: hardware reconfiguration for fast charging; six-phase system of grid

voltages obtainable from three-winding transformer with star/delta connected secondaries; single-phase charging by connecting two neutral points to the grid.

• No excitation in the first plane; only the second plane is excited.

vag

vcg

vbg

+

+

+

hardware

reconfig.

phase

transposition

three-phase

grid

S1

S2

S3

S4

iag

ibg

icg

tranformer with

two secondary sets

"1gbi

"1gci

"1 gai

"2 gbi

"2gai

"2gci

"1gbi

"1 gci

"1 gai

"2 gbi

"2 gai

"2 gci

1ai

1bi

1ci

2ai

2ci

2bi

0i

)exp(6 tjIi xy

Symmetrical six-phase topology • Propulsion: dual three-phase winding with two isolated neutral points, vector control

with two pairs of current controllers. • Charging/V2G: hardware reconfiguration for fast charging; six-phase system of grid

voltages obtainable from a transformer with open-end winding secondary; single-phase charging by connecting two neutral points directly to the grid.

• Both planes excited, but only by pulsating current:

vag

Lf, Rf

Lf, Rf

Lf, Rfvcg

vbg Lf, Rf

CBAT

+

+

+

Lf, Rf

hardware

reconfig.

phase

transposition

six-phase

machine

three-phase

grid

idc iL

ic

vdc

S1

S2

S3

Lf, RfS4

iag

ibg

icg

isolation

tranformer

1ai

1bi

1ci

2ai

2ci

2bi

1av

1bv

1cv

2av

2cv

2bv

iag"

ibg"

icg"

-iag"

-ibg"

-icg" -ibg"

iag"

-icg"

ibg"

-iag"

icg"

isolated voltage supply (off-board)

vag"

vbg"N

)cos(6 tIi )sin(6 tIji xy

Nine-phase topology and demonstrator

Single-phase charging: five-phase and six-phase systems

• In all systems with at least two neutral points single-phase supply can be connected between (any) two neutral points; no hardware reconfiguration is required.

• If phase number is an odd number, a suitable hardware reconfiguration has to be used – a single switch suffices for any odd phase number. However, different number of phases is paralleled at two sides of the single-phase supply (this impacts on the control).

Efficiency testing results: single-phase grid

-1500 -1000 -500 0 500 1000 150050

55

60

65

70

75

80

85

90

95

100Efficiency of single-phase charging IM

Power drawn from the grid (W)

Eff

icie

ncy (

%)

NoIntNoDc

WIntNoDc

NoInt

Wint

-1500 -1000 -500 0 500 1000 150050

55

60

65

70

75

80

85

90

95

100Efficiency of single-phase charging PMSM

Power drawn from the grid (W)

Eff

icie

ncy (

%)

NoIntNoDc

WIntNoDc

NoInt

Wint

Efficiency results obtained with and without interleaving for charging/V2G, and with and without the dc-dc converter:

Induction machine Permanent magnet machine

-4000 -3000 -2000 -1000 0 1000 2000 3000 400050

55

60

65

70

75

80

85

90

95

100Efficiency of three-phase charging IM

Power drawn from the grid (W)

Eff

icie

ncy (

%)

NoIntNoDc

WIntNoDc

NoInt

Wint

-4000 -3000 -2000 -1000 0 1000 2000 3000 400050

55

60

65

70

75

80

85

90

95

100Efficiency of three-phase charging PMSM

Power drawn from the grid (W)

Eff

icie

ncy (

%)

NoIntNoDc

WIntNoDc

NoInt

Wint

Efficiency testing results: three-phase grid

Efficiency results obtained with and without interleaving for charging/V2G, and with and without the dc-dc converter:

Induction machine Permanent magnet machine

Thank you for your advice during project running!

What’s next: We are keen and are looking for partners to take the solution(s) to TR5-TRL6 level through APC or Innovate UK or H2020

calls: if interested, please contact us!

Contact: Emil Levi E.Levi@ljmu.ac.uk

Liverpool John Moores University